#include <mcp/transport/http_transport.h>
#include <mcp/error.h>
#include <mcp/json/value.h>

#include <iostream>
#include <sstream>
#include <chrono>
#include <memory>
#include <thread>
#include <regex>

// For HTTP client functionality
// In a real implementation, this would use libcurl or similar
#include <vector>
#include <map>

namespace mcp {
namespace transport {

// HTTP client simulation for demonstration
class HttpClientSim {
public:
    static std::string post(const std::string& url, const std::string& data, const std::map<std::string, std::string>& headers) {
        // Simulate HTTP POST request
        // In a real implementation, this would use libcurl or similar
        std::ostringstream response;
        response << "HTTP/1.1 200 OK\r\n";
        response << "Content-Type: application/json\r\n";
        response << "Content-Length: " << data.size() << "\r\n";
        response << "Access-Control-Allow-Origin: *\r\n";
        response << "\r\n";
        response << data;
        return response.str();
    }

    static std::string get(const std::string& url) {
        // Simulate HTTP GET request
        std::ostringstream response;
        response << "HTTP/1.1 200 OK\r\n";
        response << "Content-Type: application/json\r\n";
        response << "Content-Length: 2\r\n";
        response << "\r\n";
        response << "{}";
        return response.str();
    }
};

// HttpTransport implementation
struct HttpTransport::Impl {
    HttpConfig config;
    std::atomic<bool> running{false};
    std::atomic<bool> connected{false};
    std::unique_ptr<std::thread> receiver_thread;
    MessageHandler message_handler;
    ErrorHandler error_handler;
    CloseHandler close_handler;
    OpenHandler open_handler;
    mutable std::mutex transport_mutex;

    Impl(const HttpConfig& cfg) : config(cfg) {}

    void start_listening();
    void stop_listening();
    void handle_request(const std::string& request);
    std::string generate_response(const json::Value& message);
    std::string handle_cors_preflight();
};

HttpTransport::HttpTransport(const HttpConfig& config) : impl_(std::make_unique<Impl>(config)) {}

HttpTransport::HttpTransport(uint16_t port) : impl_(std::make_unique<Impl>(HttpConfig{.port = port})) {}

HttpTransport::~HttpTransport() {
    stop();
}

bool HttpTransport::start() {
    std::lock_guard<std::mutex> lock(impl_->transport_mutex);

    if (impl_->running) {
        return true;
    }

    impl_->running = true;
    impl_->connected = true;

    // Start the listening thread
    impl_->receiver_thread = std::make_unique<std::thread>([this]() {
        impl_->start_listening();
    });

    // Notify open handler
    if (impl_->open_handler) {
        impl_->open_handler();
    }

    return true;
}

void HttpTransport::stop() {
    std::lock_guard<std::mutex> lock(impl_->transport_mutex);

    if (!impl_->running) {
        return;
    }

    impl_->running = false;
    impl_->connected = false;

    // Stop the listening thread
    impl_->stop_listening();

    if (impl_->receiver_thread && impl_->receiver_thread->joinable()) {
        impl_->receiver_thread->join();
        impl_->receiver_thread.reset();
    }

    // Notify close handler
    if (impl_->close_handler) {
        impl_->close_handler();
    }
}

bool HttpTransport::is_connected() const {
    return impl_->connected;
}

bool HttpTransport::send(const json::Value& message) {
    if (!impl_->running || !impl_->connected) {
        return false;
    }

    try {
        std::string serialized = message.serialize();
        std::string url = get_url();

        // Prepare headers
        std::map<std::string, std::string> headers = impl_->config.headers;
        headers["Content-Type"] = "application/json";
        headers["User-Agent"] = "MCP-CPP/1.0.0";

        // Send HTTP request
        HttpClientSim::post(url, serialized, headers);
        impl_->bytes_written += serialized.size();
        return true;
    } catch (const std::exception& e) {
        if (impl_->error_handler) {
            impl_->error_handler(Error::network_error(e.what()));
        }
        return false;
    }
}

std::coroutine_handle<> HttpTransport::send_async(const json::Value& message) {
    // For HTTP transport simulation, send_async behaves the same as send
    // In a real implementation, this would use async HTTP client
    send(message);
    return std::noop_coroutine();
}

void HttpTransport::set_message_handler(MessageHandler handler) {
    impl_->message_handler = std::move(handler);
}

void HttpTransport::set_error_handler(ErrorHandler handler) {
    impl_->error_handler = std::move(handler);
}

void HttpTransport::set_close_handler(CloseHandler handler) {
    impl_->close_handler = std::move(handler);
}

void HttpTransport::set_open_handler(OpenHandler handler) {
    impl_->open_handler = std::move(handler);
}

std::string HttpTransport::get_type() const {
    return "http";
}

json::Value HttpTransport::get_capabilities() const {
    json::Value capabilities = json::Value::object();
    capabilities["type"] = "http";
    capabilities["supports_async"] = true;
    capabilities["supports_compression"] = true;
    capabilities["cors_enabled"] = impl_->config.enable_cors;
    capabilities["max_request_size"] = static_cast<int64_t>(impl_->config.max_request_size);
    capabilities["max_response_size"] = static_cast<int64_t>(impl_->config.max_response_size);
    return capabilities;
}

std::string HttpTransport::get_url() const {
    std::ostringstream ss;
    ss << "http://" << impl_->config.host << ":" << impl_->config.port << impl_->config.path;
    return ss.str();
}

uint16_t HttpTransport::get_port() const {
    return impl_->config.port;
}

void HttpTransport::update_config(const HttpConfig& config) {
    std::lock_guard<std::mutex> lock(impl_->transport_mutex);
    impl_->config = config;
}

const HttpConfig& HttpTransport::get_config() const {
    return impl_->config;
}

void HttpTransport::Impl::start_listening() {
    while (running) {
        try {
            // Simulate HTTP server listening
            // In a real implementation, this would bind to a port and accept connections
            std::this_thread::sleep_for(std::chrono::milliseconds(100));

            // For demonstration, we'll just simulate handling a request
            std::string simulated_request = "POST / HTTP/1.1\r\nContent-Type: application/json\r\n\r\n{\"method\":\"test\"}";
            handle_request(simulated_request);
        } catch (const std::exception& e) {
            if (error_handler) {
                error_handler(Error::network_error(e.what()));
            }
        }
    }
}

void HttpTransport::Impl::stop_listening() {
    // No specific action needed for simulation
    // The loop in start_listening will exit when running is false
}

void HttpTransport::Impl::handle_request(const std::string& request) {
    // Parse HTTP request
    std::istringstream iss(request);
    std::string method, path, version;

    if (!(iss >> method >> path >> version)) {
        if (error_handler) {
            error_handler(Error::protocol_error("Invalid HTTP request"));
        }
        return;
    }

    // Handle CORS preflight requests
    if (method == "OPTIONS" && config.enable_cors) {
        std::string response = handle_cors_preflight();
        // In a real implementation, send response back to client
        return;
    }

    // Extract headers and body
    std::string line;
    std::map<std::string, std::string> headers;
    std::string body;

    while (std::getline(iss, line) && line != "\r") {
        size_t colon_pos = line.find(':');
        if (colon_pos != std::string::npos) {
            std::string key = line.substr(0, colon_pos);
            std::string value = line.substr(colon_pos + 1);
            // Trim whitespace
            value.erase(0, value.find_first_not_of(" \t"));
            value.erase(value.find_last_not_of(" \r\n") + 1);
            headers[key] = value;
        }
    }

    // Get the body
    std::getline(iss, body);

    // Parse JSON message
    try {
        auto result = json::Value::parse(body);
        if (result && message_handler) {
            message_handler(*result);
        } else if (!result && error_handler) {
            error_handler(result.error());
        }
    } catch (const std::exception& e) {
        if (error_handler) {
            error_handler(Error::parse_error(e.what()));
        }
    }
}

std::string HttpTransport::Impl::generate_response(const json::Value& message) {
    std::ostringstream response;
    std::string body = message.serialize();

    response << "HTTP/1.1 200 OK\r\n";
    response << "Content-Type: application/json\r\n";
    response << "Content-Length: " << body.size() << "\r\n";

    // Add CORS headers if enabled
    if (config.enable_cors) {
        response << "Access-Control-Allow-Origin: " << config.cors_origin << "\r\n";
        response << "Access-Control-Allow-Methods: POST, GET, OPTIONS\r\n";
        response << "Access-Control-Allow-Headers: Content-Type\r\n";
    }

    response << "\r\n";
    response << body;

    return response.str();
}

std::string HttpTransport::Impl::handle_cors_preflight() {
    std::ostringstream response;

    response << "HTTP/1.1 204 No Content\r\n";
    response << "Access-Control-Allow-Origin: " << config.cors_origin << "\r\n";
    response << "Access-Control-Allow-Methods: POST, GET, OPTIONS\r\n";
    response << "Access-Control-Allow-Headers: Content-Type\r\n";
    response << "\r\n";

    return response.str();
}

// HttpTransportFactory implementation
std::unique_ptr<Transport> HttpTransportFactory::create() {
    return std::make_unique<HttpTransport>();
}

std::unique_ptr<Transport> HttpTransportFactory::create_with_config(const HttpConfig& config) {
    return std::make_unique<HttpTransport>(config);
}

std::unique_ptr<Transport> HttpTransportFactory::create_with_port(uint16_t port) {
    return std::make_unique<HttpTransport>(port);
}

std::string HttpTransportFactory::get_type() const {
    return "http";
}

std::vector<std::string> HttpTransportFactory::get_supported_schemes() const {
    return {"http", "https"};
}

// Utility functions for HTTP transport
std::unique_ptr<HttpTransport> create_http_transport(uint16_t port) {
    return std::make_unique<HttpTransport>(port);
}

std::unique_ptr<HttpTransport> create_http_transport_with_config(const HttpConfig& config) {
    return std::make_unique<HttpTransport>(config);
}

HttpConfig create_http_config(const std::string& host, uint16_t port, const std::string& path) {
    HttpConfig config;
    config.host = host;
    config.port = port;
    config.path = path;
    return config;
}

} // namespace transport
} // namespace mcp